Three Part Question

In [patients requing endotracheal intubation], does [nasal oxygen administration during the apneic period] following induction increase the time to desaturation]?

Clinical Scenario

A patient in your ED requires endotracheal
intubation due to respiratory failure, refractory to non-invasive ventilation. The patient is preoxygenated with non-invasive ventilation on 100% oxygen prior to anaesthetic induction and until apnoea. During the intubation attempt,
the oxygen saturation falls significantly. This leads you to consider if additional strategies alongside optimised preoxygenation may have provided more time before desaturation during apnoea. You decide to search and appraise the currently available literature to see if the use of the so-called apnoeic oxygenation would delay critical desaturation.

Search Strategy

Ovid journals and full texts from 1985 to March 2016

Embase from 1974 to March 2016

AMED from 1985 to March 2016

HMIC from 1979 to March 2016
{(apnoeic oxygenation.mp) OR (apnoeic oxygen$.mp) OR (apneic oxygenation.mp)} OR {[(exp Oxygen Inhalation Therapy/) OR (oxygen inhalation.mp)] OR [(exp Oxygen Inhalation Therapy/) AND (exp Insufflation/)] OR [(exp Oxygen/) AND (exp Insufflation/)] AND [(exp Nasal Absorption/) OR (nasal.mp)]} AND {[(exp Intubation, Intratracheal/) OR (rapid sequence intubation.mp) OR (rapid sequence induction.mp) OR (RSI.mp)]}

ClinicalTrials.gov site for ongoing trials using the term ‘apnoeic oxygenation’.

Search Outcome

One hundred and sixty-seven papers were found using the above-described search strategy. Eight articles seemed to address our specific question. Of these one was retracted after publication and three were audit/abstract only papers. The only ongoing trial, now completed (but not published) yielded on the ClinicalTrials.gov site could not be retrieved.

Primary outcome measured was lowest SpO2 in each patient. Desaturation to <80% was expressed as a percentage of occurrence Multivariate analysis was performed and results expressed as OR and 95% CI

In nasal high flow group 2% of patients desaturated to <80% compared with 14% desaturating to <80% in the control group (p=0.03) HFNC was found to be independent protective factor against severe hypoxia OR 0.14, 95%CI 0.01 to 09, (p=0.037) Median SpO2 after pre-oxygenation with NRBM was 100% (IQR 98–100%) vs 100% (IQR 100–100%) in HFNC group p=0.01 Median lowest SpO2 in the NRBM group was 94% (IQR 83–98%) vs 100% (IQR 95–100%) in HFNC group p≤0.000

Biases of a before and after study
Higher Cormac Lehane score and lower junior resident success rate in the NRBM group may have confounded the results
Potential for recall bias as data collected by procedural operator

Position of the patient for intubation was variable
Different intubation techniques were used which may have influenced the results
50% of patients were ventilated through the apnoeic period with either BVM or BIPAP
Only 56 patients in total were not ventilated through apnoea although there was an equal distribution and manual ventilation between groups
Some of the crucial confounders in this study are only mentioned in the online supplemental data

Wimalasena, Burns, Reid et al, 2015Australia

Intubations performed by Australian Helicopter Service
Electronic registry data collected from a 22-month period pre and post the introduction of apnoeic oxygenation to the standard operating procedure for RSI
Pre-apnoeic oxygenation group, N=310
Receiving apnoeic oxygenation, N=418

Observational Trial

Oxygen saturation below 93% at any point during induction and intubation. ORs with 95% CIs

Convenience sample
No propensity matching
Larger post-apnoeic oxygenation population may have skewed results
Potential improvements in practice over the time course of the study
No description of the RSI process
Very broad CI
Data collected by procedural operator so recall bias is potentially introduced
No documentation of compliance to SOP, or if apnoeic oxygenation received

Sakles Mosier et al,2014USA

N=127 adults with intracranial haemorrhage requiring ED intubations split into two groups
N=72 in apnoeic oxygenation group
N=55, no apnoeic oxygenation group

29% (16/55) of patients in the standard care group desaturated to <90% compared with 7% (5/72) of the apnoeic oxygenation group OR 0.13 (95% CI 0.03 to 0.53)

Non-randomised, trial (intervention decided by the operator)
Data collected by the operator
Variable flow rates in the apnoeic oxygenation group
First-pass success was higher in the apnoeic oxygenation group
Different intubation techniques used

Comment(s)

For any patient requiring emergency intubation and ventilation it is crucial to optimise chances of maintaining oxygen saturations during intubation attempts.5 This involves optimal patient positioning, oxygenation techniques and optimal intubation conditions. Waiting for paralysis prevents initiation of a gag reflex upon laryngoscopy and allows maximal laryngeal exposure, increasing chances of first-pass success.5 Apnoeic oxygenation allows oxygenation and ventilation of patients during the onset phase of muscle relaxation.5
During apnoea gas exchange between the alveoli and the bloodstream still occurs.5 It is estimated that 250 mL/min of oxygen diffuse into the blood stream compared with 20 mL/min of carbon dioxide moving into the alveoli from the blood stream.5 This means pressure in the alveoli reduces creating a gradient for gas transfer from the pharynx into the alveoli.5
The majority of the retrieved and analysed papers seem to suggest that the use of apnoeic oxygenation reduces the incidence of desaturation during intubation. These studies are however very heterogeneous in terms of methodology, outcomes and most importantly populations studied so it is somewhat difficult to draw conclusions for everyday emergency medicine practice.

Clinical Bottom Line

Apnoeic oxygenation is a harmless procedure and there is emerging evidence that its use does help prevent oxygen desaturations during emergency intubation attempts. Further well-constructed and ED-based studies are however needed to explore its benefits in the ED.

Sakles JC, Mosier JM, Patanwala AE, et al. Apneic oxygenation is associated with a reduction in the incidence of hypoxemia during the RSI of patients with intracranial hemorrhage in the emergency department. Intern Emerg Med 2016 11(7):983-92.